An axon growth associated antigen is also an early marker of neuronal determination.

We have previously described the generation of a monoclonal antibody (DSS-3) that binds to all neurons in cockroach embryos at 50% development and to only a small subset of interneurons in the adult nervous system. This developmental stage-specific antigen was observed to reappear in all axotomized adult neurons that were undergoing axonal regeneration. In the present study the time course of the appearance of this growth-associated antigen during embryonic development was determined. Unexpectedly, the antigen was observed to be present in embryonic neurons long before axon growth. In addition, all cells in the CNS neuronal lineage (neuroblasts, ganglion mother cells, and neurons) bind the antibody as soon as they can be morphologically identified. However, the antigen is also transiently present in all neuroepithelial cells at a stage prior to the morphological differentiation of some of them to neuroblasts. Analogous patterns of DSS-3 binding to cells involved in the development of sensory neurons and leg pioneer neurons are observed. The DSS-3 antigen is therefore a very early marker for the capacity of ectodermal epithelial cells to develop along a neuronal lineage.